Causes of Earthquakes in Switzerland

Seismic activity in Switzerland and the formation of the Alps are closely linked. Generally speaking, the earthquakes we observe in Switzerland result from collisions between the European and African lithospheric plates, reflecting the underlying mechanics of these tectonic processes.

Seismic waves penetrate the subsurface, casting light on the nature of the deep lithosphere beneath the Alps. One important detail has been discovered in the last few years: following the complete subduction of the oceanic lithosphere and the subsequent collision of the two continents, a remnant of the original mantle lithosphere (known as the mantle slab) remains attached to the European Plate. In the northern foothills of the Alps, this slab is bending the lithosphere downwards, thereby indirectly causing widely distributed seismicity on the Swiss plateau. Since plate tectonic processes take place over geological time scales, it can be assumed that the current level of seismicity in the Alpine region will continue for millions of years to come. To learn more about this topic, see the snapshot "Earthquakes and the Alps".

Cross section through the lithosphere schematically showing the various forces acting at depth on the Alps

The hanging European slab (mantle lithosphere) causes a downward force, while the lower crust detaches from the slab and the large crustal root generates buoyancy to compensate for loads by topography (mountains) and by the slab (Singer et al. 2014, EPSL).

Three-dimensional representation of the hanging European mantle lithosphere slab

This is one of the main driving forces for earthquake activity in the Alps. The NW-SE profile that is marked in red is shown in the previous figure (Singer et al. 2014, EPSL).

Three-dimensional representation of the Adriatic mantle lithosphere

This is the other main driving force of Alpine seismicity. The geometry of the Adriatic plate is complex: in both the west and the east, it bends downward, opposite to the likewise bending European slab. Its southern end also bends downward. How the Adriatic plate overlaps Europe is shown on the bottom right (simplified from Lippitsch et al. 2003, JGR).